Bisphenol A and Other Chemicals in Plastics

Environmental Impacts on Reproductive Health

(Published January 2010)

This chapter focuses on some of the chemicals in plastics, including bisphenol A, which has been shown to have estrogen-like effects and to disrupt thyroid function in animals.

This monograph includes a discussion of the endocrinedisrupting chemical bisphenol A (BPA) for three reasons:

• Patients are requesting more information about plastics and BPA.
• Animal data suggest an increased susceptibility of the developing organism, which raises concerns about effect on the human fetus, especially during early gestation (when many women are unaware that they’re pregnant).¹
• BPA is under scrutiny by state and federal agencies, and clinicians may be asked to discuss the potential effect of BPA exposure on reproductive health with other health professionals, patient groups, policy-makers, and the media.

Sources of Bisphenol A

Bisphenol A is a chemical used in some epoxy resins and adhesives. BPA-containing resins are used in the lining of metal food and beverage cans, and the lining of such cans (e.g., soft drink, food, and infant formula cans) is a significant source of BPA in food items.^2,3 BPA is polymerized to make polycarbonate plastic. Polycarbonate is a hard clear plastic that is identified by the “other plastics” category for recycling, designated by a triangle with the number 7 often found on the underside of recyclable containers. BPA also may be added to other kinds of plastic. BPA can leach from plastic containers, devices, and medical equipment into food or beverages, especially when heated.

Now you know that the correct answer to the quiz question is A: canned vegetables are most likely to contain BPA. Food storage containers and hard plastic water bottles may contain BPA. Stretch film used in food packaging also may contain BPA.⁴ Medical equipment, including endotracheal tubes, umbilical catheters, and plastic bags containing intravenous fluids, sometimes contain BPA.³ Other potential sources of BPA include dust, PVC piping, cash register receipts, and dental composites and sealants.

Population studies have shown that BPA exposure is common in the United States. A 2008 study reported that almost 93 percent of individuals age 6 or older had detectable BPA levels in their urine.³ Levels were higher in children than adults (see Figure 10). In addition, human studies have shown that interventions to reduce exposure to BPA do decrease blood BPA levels.

Testing in various countries has found BPA in canned foods, such as vegetables, soups, fruits, meat products, fish, and desserts.⁷ Plastic baby bottles and liquid baby formula (i.e., not powdered) may also contain BPA.^6,7

Data on the Reproductive Health Impact of Bisphenol A

Laboratory research has demonstrated that BPA is an estrogen receptor agonist and blocks both androgen and thyroid hormone receptors.⁸ Studies in animals have shown that BPA exposure is associated with early puberty in females, lower sperm counts, and increased susceptibility to reproductive tract cancers and altered brain development in males and females.^8-13 More recently, BPA has been associated with diabetes and cardiovascular disease in humans.¹⁴

Definitive data linking BPA exposure to specific pathological conditions in humans are not yet available. However, some of the adverse effects in animal studies are observed at levels of exposure close to those common in people. For this reason, clinicians, scientists, and consumer activists are concerned, even if the effects are not yet clearly documented in humans. Given the strength of the emerging data, many experts believe that it is prudent to recommend now that patients reduce BPA exposure and to provide clinicians with tools to help patients reduce their risk of exposure.

Other Chemicals in Plastics

In addition to BPA, other chemicals associated with plastics have raised concerns. These include phthalates and polyvinyl chloride (PVC). Phthalates are plastizicers, substances added to plastics or other materials to make them more pliable.¹⁵These chemicals are used to create building materials, packaging, and plastic toys. They also are ingredients in personal care products, such as cosmetics, shampoos, and perfumes, and in some pharmaceuticals. A small (n = 145) pilot study in humans recently showed that preschool boys whose mothers during pregnancy had higher urinary concentrations of two common phthalates were less likely to engage in typically male play (e.g., play fights) than boys whose mothers had lower urinary levels during pregnancy.¹⁶ Previous research has shown that gender-related play behavior reflects the effects of endocrine-disrupting chemicals, such as PCBs.

Hundreds of studies in laboratory animals have shown that the developing male reproductive tract is particularly sensitive to exposure to some phthalates. The exposures that cause these effects are much lower than those necessary to cause effects in adults. Some adults are exposed to those phthalates at levels that approach those that cause effects in laboratory animals. Preliminary data from the first human studies have shown concerning reproductive health effects with phthalate exposure, relating to their endocrine-disrupting effects. One study found a smaller anogenital distance (AGD), which is the span between the anus and the genitals and a marker for feminization, in the male infants of women with higher urinary levels of phthalates.¹⁷ Reduced AGD is a marker for prenatal exposure to androgen antagonists (anti-androgens). A follow-up study found that the serum levels of phthalates in the mothers of male infants with reduced AGD were actually lower than the Environmental Protection Agency’s designated reference doses for these chemicals; in other words, these problems were manifesting in the offspring of women whose phthalate levels were within the range considered “safe.”¹⁵Several preliminary studies have found inconsistent effects on birth—either delaying birth or increasing the chance of premature birth. Although one cannot make a firm conclusion about the clinical significance of these findings, the results suggest that exposure to phthalates may result in changes in reproductive tract development. Therefore, clinicians can exercise precaution and recommend ways their patients can limit exposure to phthalates.

Polyvinyl chloride, a type of plastic, is a polymer used to manufacture a variety of products including pipes, wire and cable coatings, building materials, and packaging materials.¹⁸ It also is used in some household items, such as shower curtain liners, furniture and automobile upholstery, wall coverings, housewares, and automotive parts.¹⁹ Depending on the application, other substances are often added. Phthalates make a polymer less brittle. Heavy metals are often added as stabilizers.²⁰ These substances can leach from PVC-containing products (e.g., if a child sucks on an object) or be released into the air (e.g., from new shower curtain liners).

The next chapter highlights helpful environmental health resources for providers and patients.

References:

1. vom Saal FS, Hughes C. An extensive new literature concerning low-dose effects of bisphenol A shows the need for a new risk assessment. Environ Health Perspect. 2005;13:926–33.
2. Parker-Pope T. A hard plastic is raising hard questions. New York Times. April 22, 2008. Available at: http://www.nytimes.com/2008/04/22/health/22well.html. Accessed January 10, 2010.
3. Calafat AM, Weuve J, Ye X, et al. Exposure to bisphenol A and other phenols in neonatal intensive care unit premature infants. Environ Health Perspect. 2009;117(4):639–44.
4. Lopez-Cervantes J, Paseiro-Losada P. Determination of bisphenol A in, and its migration from, PBV stretch film used for food packaging. Food Addit Contam. 2003;20:596–606.
5. Calafat AM, Ye X, Wong LY, et al. Exposure of the U.S. population to bisphenol A and 4-tertiary-octylphenol: 2003–2004. Environ Health Perspect. 2008; 116:39–44.
6. Food and Drug Administration. Draft assessment of bisphenol A for use in food contact applications. August 2008. Available at: http://www.fda.gov/ohrms/dockets/AC/08/briefing/2008-0038b1_01_02_FDA%20BPA%20Draft%20Assessment.pdf. Accessed September 10, 2009.
7. National Toxicology Program. US Department of Health and Human Services. NTP-CERHR Expert Panel Report on the Reproductive and Developmental Toxicity of Bisphenol A. 2007. Available at: http://cerhr.niehs.nih.gov/chemicals/bisphenol/BPAFinalEPVF112607.pdf. Accessed October 12, 2009.
8. Newbold RR, Jefferson WN, Padilla-Banks E. Prenatal exposure to bisphenol A at environmentally relevant doses adversely affects the murine female reproductive tract later in life. Environ Health Perspect. 2009;117(6):879–85.
9. Jenkins S, Raghuraman N, Eltoum I, et al. Oral exposure to bisphenol A increases dimethylbenzanthracene-induced mammary cancer in rats. Environ Health Perspect. 2009;117(6):910–5.
10. Ho SM, Tang WY, Belmonte de Frausto J, Prins GS. Developmental exposure to estradiol and bisphenol A increases susceptibility to prostate carcinogenesis and epigenetically regulates phosphodiesterase type 4 variant 4. Cancer Res. 2006;66(11):5624–32.
11. Howdeshell KL, Hotchkiss AK, Thayer KA, et al. Exposure to bisphenol A advances puberty. Nature. 1999;401(6755):763–4.
12. Chapin RE, Adams J, Boekelheide K, et al. NTP-CERHR Expert panel report on the reproductive and developmental toxicity of bisphenol A. Birth Defects Research. 2008;83:157–395.
13. Leranth C, Hajszan T, Szigeti-Buck K,et al. Bisphenol A prevents the synaptogenic response to estradiol in hippocampus and prefrontal cortex of ovariectomized nonhuman primates. Proc Natl Acad Sci U S A. 2008;105(37):14187–91.
14. Lang IA, Galloway TS, Scarlett A, et al. Association of urinary bisphenol A concentration with medical disorders and laboratory abnormalities in adults. JAMA. 2008;300(11):1303–10.
15. Marsee K, Woodruff TJ, Axelrad DA,etl al. Estimated daily exposures in a population of mothers of male infants exhibiting reduced anogenital distance. Environ Health Perspect. 2006;114:805–9.
16. Swan SH, Liu F, Hines M, et al. Prenatal phthalate exposure and reduced masculine play in boys. Int J Androl. 2009 Nov 16. [Epub ahead of print]
17. Swan SH, Main KM, Liu F, et al. Decrease in anogenital distance among male infants with prenatal phthalate exposure. Environ Health Perspect. 2005;113:1056–61.
18. Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for Vinyl Chloride (Update). Atlanta, GA: Public Health Service, US Department of Health and Human Services. 1997.
19. Environmental Protection Agency. Vinyl Chloride: Hazard Summary. 2000. Available at: http://www.epa.gov/ttn/atw/hlthef/vinylchl.html. Accessed October 13, 2009.
20. Thornton J. Environmental Impacts of Polyvinyl Chloride Building Materials. Healthy Building Network. 2002. Available at: http://www.healthybuilding.net/pvc/Thornton_Enviro_Impacts_of_PVC.pdf. Accessed October 13, 2009.
21. University of California-San Fransisco, Program on Reproductive Health and the Environment. Toxic matters. Available at: http://www.prhe.ucsf.edu/prhe/index.html. Accessed December 26, 2009.
22. Center for Health, Environment and Justice. Volatile vinyl: the new shower curtain’s chemical smell. June 2008. Available at: http://www.chej.org/documents/VolatileVinyl.pdf. Accessed September 9, 2009.
23. Natural Resources Defense Council. Chemicals in plastic bottles: how to know what’s safe for your family. May 2008. Available at: http://www.nrdc.org/health/bpa.pdf. Accessed August 27, 2009.